Piston ring



D. W- HAMM PISTON RING Sept. 14, 1965 2 Sheets-Sheet 1 Filed March 18, 1965 .30 5 30 Wamnmmumwfl Mummmw FIG. 5,

INVENTOR. 9006145 4/ HAM/4 BY I ac M

Sept. 14, 1965 D. w. HAMM 3,206,219

' PISTON RING Filed March 18, 1963 2 Sheets-Sheet 2 INVENTOR 0406145 4/ #41? BY 2W United States Patent 3,206,219 PISTON RING Douglas W. Hamrn, Norton Township, Muskegon County, Mich assignor to Muskegon Piston Ring Company, Muskegon, Mich, a corporation of Michigan Filed Mar. 18, 1963, Ser. No. 265,777 Claims. (Cl. 277-215) This invention relates to piston rings, and more particularly to an oil ring of novel construction.

In modern automotive engines, it is conventional to use an oil ring having a pair of rails supported by a spacer-expander. The rails make contact with the cylinder wall, and seat against the sides of the ring groove to perform the sealing action. The spacer-expander holds the rails in position, and by virtue of its radial tension biases the rails outwardly to conform to the cylinder wall.

The conventional rail and spacer-expander combination has a number of shortcomings which this invention is designed to overcome. in the first place, with the conventional rail and spacer-expander combination, wear occurs on the rails at the point of contact with the cylinder wall. It also occurs at each of the points of con tact between the rail and the ears on the spacer-expander which bear against the inner face of the rail for transmitting the tension of the spacer-expander to the rail. Thus, in each such ring utilizing two rails and a spacerexpander, there are eight points of wear or four per rail. As the wear increases at each of these points, the effective wall thickness of the rail is reduced, both upsetting the initial radial tension balance of the ring, and the total radial tension exerted by the ring. The reduction in radial tension is serious because it reduces the sealing eificiency of the ring.

The substitution of a simple U-shaped ring, having no rails, materially reduces the significance of this problem because it cuts the number of points of wear by fifty percent. Thus, the ring has a significantly longer life and maintains its functional efiiciency for a greater proportion of this extended life. Such U-shaped rings, eliminating the use of the rails, are of course old and wellknown. There is no invention in simply substituting such a ring for a more conventional rail and spacerexpander combination type ring. However, despite the obvious advantages, such rings have not proved sufiiciently satisfactory in service to have permitted there general acceptance.

The difficulty has arisen from the fact that such rings have always been made of materials of uniform thickness or cross-sectional characteristics throughout their entire cross section. The dificulty has arisen with the land segment portions of the ring, i.e. the portion of the ring which is at the radially outer portion and bears against the cylinder walls. When a material is selected of a wall thickness suitable to impart to the springs or radially inner portion of the ring the required resilience, the strength of the material is inadequate to provide a land segment capable of withstanding the deflection loads imposed upon it. When a material is selected of sufficient wall thickness to provide land segments of adequate strength, the inner radial portion of the ring becomes too stiff and unyielding to provide a ring of the required flexibility and radial tension values.

This invention overcomes this problem by reinforcing the outer radial portion or land segment portion of the ring without necessitating an increase in material Wall thickness of the inner radial or spring portion of the ring. A ring constructed according to this invention combines the characteristics of high strength in the land portion with the flexibility in the spring portion required to im part to the ring the proper radial tension and conformice ability characteristics necessary for efficient operation.

In rings of this type in which the land segments are not reinforced, experience has shown that they have a tendency to buckle axially when the ring is closed and circumferentially compressed to create the desired radial tension. Experience has also shown that the corners of the land segments have a tendency to become bent due to the high loading factor imposed on the rings during engine operation. This invention provides a ring which eliminates these problems.

These and other objects and purposes of this invention will be immediately understood by those acquainted with the design and manufacture of piston rings upon reading the following specification and the accompanying drawings.

In the drawings:

FIG. 1 is a fragmentary oblique view of a ring constructed according to this invention.

FIG. 2 is a fragmentary view of a blank for a ring prior to bending to final configuration.

FIG. 3 is a sectional view taken along the plane IILJH of FIG. 2.

FIG. 4 is a sectional view similar to FIG. 3 showing a modified blank.

FIGS. 5, 6 and 7 are sectional views similar to FIG. 3 showing further modified blanks.

FIG. 8 is a fragmentary sectional view of a ring embodying this invention installed in the ring groove of a piston.

FIGS. 9, 10 and ll are views sirnilar to FIG. 8 but showing the several modified forms of the ring installed in the ring groove of a piston.

FIG. 12 is a fragmentary, elevation view of a prior art ring illustrating the condition of the ring after a period of operation (the deflection of the land segments being exaggerated to permit illustration).

In executing the objects and purposes of this invention there is provided a ring in which the thickness of the material used to form the sides of the ring is substantially greater than that of the material used to form the strut or inner bight portion of the ring. This thickness may be provided by use of a material thickened in the portions which become the sides, or a material which is off-set in the portions which become the sides to, in effect, form a stiffening rib in this section of the ring body.

Referring specifically to the drawings, the numeral 10 indicates a blank, which is best illustrated in FIG. 2, having a central portion 11 substantially thinner than the two marginal portions 12 and 12a. An example of a satisfactory material for this ring is a blank with side portions 12 and 12a having a thickness of approximately 0.04 of an inch and a central portion 11 of approximately 0.025 of an inch. These dimensions are not to be considered as limitations but only as illustrative. The blank 10 is a continuous ribbon of material which may be formed to the selected cross-sectional configuration by any of several well-known methods none of which forms a part of this invention.

The ribbon is processed to form the elongated slots 13 and 13a in the thinner central portion of the blank. The slots 13 and 13a are identical except that the slots 13a have their V-shaped points directed oppositely to the slots 13. The slots 13 and 13a are arranged in an alternate pattern along the ribbon having narrow strips of material between them.

Extending outwardly from the V-shaped point of each of the slots 13 and 13a is an embossment 14. This embossment locates and facilitates the formation of the cracked partings which are formed in the ring after the ring has been shaped. The nature of the slots 13 and of the embossments 14 is known and does not form a part of this invention. The outer edge margins of the blank 10 may be chamfered at to reduce the thickness of the material bearing against the cylinder wall, facilitating break-in or seating of the ring when it is initially operated in the engine. This again is known and does not form a part of this invention.

The blank is passed through suitable dies to form it into a U-shaped member as illustrated in FIGS. 1 and 8.

In this forming, the thicker portions 12 and 12a of the ring become the sides of the ring 16. The strips of material which remain between the slots 13 and 13a become the struts 17 of the ring. These are formed entirely from the thinner central portion of the blank. The thinner central portion of the blank also extends into the sides of the ring as is indicated in FIGS. 1 and 8.

The finished ring is coiled into a circle and has a part at 18 (FIG. 1). This is open when the ring is free, but i closed when the ring is confined within a cylinder. The sides of the ring are cracked at each of the embossments 14 to separate the outer radial portions of the ring into a plurality of individual land segments 19. Thus, each segment is separated from each adjacent segment by a severance line 20 resulting from the cracking. Each of these segments is connected to two of the struts 17 with the segments on the upper and lower sides of the ring being off-set circumferentially so that each of the struts of the pair which are connected to a single segment on one side of the ring are integral with different segments on the opposite side of the ring. Thus, the ring body is a continuous integral element but its continuity zig-zags back and forth between the sides.

FIG. 4 illustrates the fact that the entire additional material thickness in the marginal portions of the blank may be provided on a single face of the blank rather than provided equally on both faces of the blank as shown in FIG. 3. Thus, while the blank 10a has a central portion 11 which is thinner than the edge portions 12b and 12c, the entire added thickness of the edge portions 12b and 120 is provided on one face of the blank leaving one surface of the blank flat. The blank 10:: may be rolled in such a manner that the thickened portions of the margins 12b and 12c are located within the ring 17a and therefore face each other as suggested in FIG. 9. Alternately, the ring 17b may be so formed that they project outwardly as suggested in FIG. 10.

In effect, the additional thickness provided in the sides of the ring can be considered as a reinforcing rib. In blank 10a, the rib projects from one side of the ring and in blank 10 a pair of ribs are provided which project from opposite sides of the ring.

FIG. 5 shows a blank 1% in which the material thickness is uniform across the blank. However, adjacent the marginal edges, the blank is rolled or otherwise processed to form a shallow, U-shaped rib 30 with the ribs on both sides projecting in the same direction. FIG. 6 illustrates a blank 10c in which the same general rib formation is used, but the ribs 31 are substantially wider and occupy almost all of the marginal portions of the blank outwardly of the ends of the slots 13 and 13a.

FIG. 7 illustrates a blank 10d of the same general characteristics as blanks 10b and 10c, but which has been processed to provide oppositely projecting ribs 32 and 33 in each side margin. Such an arrangement will increase the stiffness of the segments of the finished ring substantially over those of the configuration of blanks 1% and 10c.

The ribs 30 and 31 or 32 and 33 serve to stiffen these edge portions in the same manner that corrugating a sheet serves to stiffen the sheet by materially increasing the moment of inertia of the structure to resist bending of these edge portions lengthwise of the blank, and thus circumferentially of the finished ring. The stiffening effect is resistant to circumferential compression since these ribs extend circumferentially of the finished rings. It will be understood that the blanks 16b and 100 may be formed into rings with the ribs projecting either inwardly or out- 4 wardly of the faces of the rings in the same manner as FIGS. 9 and 10 suggest that this be done where the thickness of the edge margins is concentrated on one face of the blank. FIG. 11 illustrates a ring formed upon the blank 10c with the ribs 31 projecting outwardly.

As previously stated, the ring in its free state has an open part. When the ring is placed in a cylinder, this part or gap is closed, and the ring is slightly compressed circumferentially. This compression is most important because it creates the necessary radial tension which causes the ring to seat against and form a sealing fit with the cylinder wall 53. The U-shaped nature of the ring and the resilient material from which it is made, cause the ring in this condition to act like a spring. The closing of the gap and the placing of the ring on radial compression assures conformability of the ring to the cylinder walls as the piston reciprocates.

It is important that the degree of circumferential compression and radial tension be maintained throughout the life of the ring. Failure to do so will produce a ring which gradually loses its effectiveness as a sealing member. FIG. 12 illustrates what experience has shown happens to conventional rings after a period of time. The land segments 49, because of insuflicient circumferential strength, tend to relieve the circumferential pressure by becoming arched or deflected. While the amount of arching or deflection is considerably exaggerated in FIG. 12

in order to permit illustration, this deflection or bending is suflicient to unseat the edges of the segments from the sides 41 and 41a of the ring groove 42 creating a plurality of small channels 43 through which lubricants and gases are permitted to bypass the seal of the ring. Thesechan- .nels 43, although quite small, collectively greatly reduce the efiiciency of the ring. Once the segments have started to arch, the arching effect will increase at an accelerated rate because even the slightest arch, once formed, tends to destroy the beam effect of the land segments in resisting compressive loads. It will continue until all or a major portion of the circumferential compression of the ring has been released. At this point, not only does the ring have poor sealing effect against the sides of the ring groove, but it also has insufficient tension to form a seal against the cylinder wall. Thus, the ring as a whole becomes ineffective and requires replacement.

Rings of this type of conventional structure, when closed, tend to buckle or snake, that is, distort axially. Such a ring, when installed, tends to press against the sides of the grooves. The resulting friction restricts the flexing action of the ring, tending to make it sluggish and unresponsive. This materially reduces its sealing efiiciency.

This invention overcomes this problem by giving the rings sulficient axial stability that when closed they remain flat in the plane of the ring groove. Thus, they have substantially constant and predeterminable bearing pressure against the side of the ring groove giving them freedom of response to conformability requirements. This alone is a material improvement over conventional ring designs.

Another effect of this arching of segments of conventional rings is the opening of the parting lines 44 between the land segments. As the arching increases and the tension goes out of the ring, these partings tend to open up, creating numerous openings by which gases and lubricants can pass directly through the ring. This eficct is cumulative and merely emphasizes the effect of the ends of the land segments unseating from the sides of the ring groove.

As will be seen from FIGS. 8 through 11, when the ring is seated in a ring groove 50, its inner radial face is spaced from the bottom or root 51 of the ring groove. The land segment portions seat against the sides 52 and 52a of the ring groove. This seating action is such that there is no bind between the sides of the ring and the sides of the groove because it is necessary that the ring be free to move radially in order to conform to the cylinder walls 53 as the piston reciprocates. It will be noted from each of these figures, that the reinforced portion of the ring structure is the portion which forms the seat with the sides of the ring groove. It will also be noted that it is basically the reinforced portion which is exposed to the compressive forces of gases in the area between the cylinder wall and the face of the piston. Thus, the reinforcement of the land segments, either by the use of material which is thicker at this point, ora material which has been shaped to form a rib structure, provides support at the point of maximum loading of the ring.

At the outer diameter of the ring, it is not only subjected to the circumferentially acting compressive forces attendant the closing of the ring but also to the drag created by the sliding of the outer face of the ring along the cylinder wall, as well as the compressive effect of gases which are attempting to escape between the cylinder wall and the piston. Thus, a ring constructed according to this invention has the reinforcement necessary to withstand these combined forces at the point of maximum application of the forces. At the same time, the radially inner portion of the ring remains flexible whereby the ring has the necessary flexibility for conformity and the necessary degree of resilience to provide the proper radial tension. Such a ring will retain its sealing characteristics throughout a considerably increased life span.

While a preferred embodiment of this invention, together with several modifications, have been described, it will be recognized that other modifications may be made, each within the scope of the invention, and embodying the principles of the invention. Such of these modifications as embody the principles of the invention are to be considered as included in the hereinafter appended claims, unless these claims by their language expressly state otherwise.

I claim:

1. A piston ring having a body formed from a single piece of material of uniform thickness, said body being of U-shaped cross section with the free ends of the legs thereof extending radially outwardly; the radially outer portions of said body adjacent the edges thereof each being offset to form an axially extending rib therein increasing the thickness thereof effective in resisting bending for reinforcing said radially outer portions of said body against deflection in an axial direction; the rib on each of said legs of the U-shaped body projecting away from the rib on the other of said legs.

2. A piston ring as recited in claim 1 wherein the ribs on each of said legs has an axially projecting crown, the axially outer faces of said crowns being flattened for forming an annular ring groove contacting surface.

3. A piston ring as recited in claim 1 wherein each of said legs are offset in opposite directions forming ribs projecting from both axial faces of both of said legs of the U-shaped body.

4. A piston ring as recited in claim 3 wherein said oppositely offset ribs are in side by side relationship to each other circumferentially of said ring.

5. In combination, a piston having a ring groove characterized by size and an oil ring having a body formed from a single piece of material of uniform thickness, said body being of U-shaped cross section with the free ends of the legs thereof extending radially outwardly adjacent the sides of said ring groove; the radially outer portions of said legs adjacent the ends thereof each being offset to form an axially extending rib therein increasing the thickness thereof effective in resisting bending for reinforcing said radially outer portions of said body against deflection in a axial direction; each of said ribs having an axially projecting crown portion extending toward the sides of said ring groove, said crown portions of said ribs forming the portions of the sides of said ring making sealing contact with the sides of the ring groove when said ring is seated therein, said crown portions spacing the remainder of said legs from the sides of said ring groove.

References Cited by the Examiner UNITED STATES PATENTS 2,280,743 4/42 Bowers 2772l5 2,296,332 9/42 Bowers 277-215 2,346,204 4/44 Bowers 277200 3,053,545 9/62 Knocke 277202 LEWIS J. LENNY, Primary Examiner.

EDWARD V. BENHAM, Examiner. 

1. A PISTON RING HAVING A BODY FORMED FROM A SINGLE PIECE OF MATERIAL OF UNIFORM THICKNESS, SAID BODY BEING OF U-SHAPED CROSS SECITON WITH THE FREE ENDS OF THE LEGS THEREOF EXTENDING RADIALLY OUTWARDLY; THE RADIALLY OUTER PORTIONS OF SAID BODY ADJACENT THE EDGES THEREOF EACH BEING OFFSET TO FORM AN AXIALLY EXTENDING RIB THEREIN INCREASING THE THICKNESS THEREOF EFFECTIVE IN RESISTING BENDING FOR REINFORCING SAID RADIALLY OUTER PORTIONS OF SAID BODY AGAINST DEFLECTION IN AN AXIAL DIRECTION; THE RIB ON EACH OF SAID LEGS OF THE U-SHAPED BODY PROJECTING AWAY FROM THE RIB ON THE OTHER OF SAID LEGS. 